The present disclosure relates generally to infrared detection, and more particularly to systems for use in detecting multiple infrared bands using a barrier-type detector.
At least some known infrared detectors include a barrier layer that is coupled to a single absorption layer that generates an electrical current after receiving infrared radiation in a predetermined wavelength band. In such detectors, the barrier layer is fabricated from a uniform material that is aligned with valence band energy levels of the single absorption layer. Accordingly, the uniform barrier layer is not suitable for concurrent use with a second absorption layer that is sensitive to a different wavelength band if the valence band edge of the second absorbing layer is not naturally aligned with that of the first absorbing layer.
The response of an infrared detector is a function of an operating bias voltage that is applied to the device structure. Misalignments in valence band energy levels of a barrier layer and an absorption layer can be remedied, to an extent, by adjusting a magnitude of a bias voltage applied to the device structure. However, applying a bias voltage beyond about 500 millivolts (mV) may create an increase in dark current that reduces performance of the detector and reduces the ability of the infrared detector to accurately detect infrared radiation. As such the use of infrared detectors may be limited.
Achieving proper alignment of the valence band energy levels of barrier layers and multiple absorbing layers in a detector structure designed for detection of infrared radiation in multiple spectral bands is highly desirable.